Evidence that human blastomere cleavage is under unique cell cycle control

J Assist Reprod Genet. 2009 Apr;26(4):187-95. doi: 10.1007/s10815-009-9306-x. Epub 2009 Mar 14.


Purpose: To understand the molecular pathways that control early human embryo development.

Methods: Improved methods of linear amplification of mRNAs and whole human genome microarray analyses were utilized to characterize gene expression in normal appearing 8-Cell human embryos, in comparison with published microarrays of human fibroblasts and pluripotent stem cells.

Results: Many genes involved in circadian rhythm and cell division were over-expressed in the 8-Cells. The cell cycle checkpoints, RB and WEE1, were silent on the 8-Cell arrays, whereas the recently described tumor suppressor, UHRF2, was up-regulated >10-fold, and the proto-oncogene, MYC, and the core element of circadian rhythm, CLOCK, were elevated up to >50-fold on the 8-Cell arrays.

Conclusions: The canonical G1 and G2 cell cycle checkpoints are not active in totipotent human blastomeres, perhaps replaced by UHRF2, MYC, and intracellular circadian pathways, which may play important roles in early human development.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blastomeres / physiology*
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • Cell Cycle*
  • Cell Division
  • Circadian Rhythm
  • DNA Replication
  • Female
  • Fibroblasts / metabolism
  • Humans
  • Male
  • Oligonucleotide Array Sequence Analysis
  • Pluripotent Stem Cells / metabolism
  • RNA, Messenger / metabolism*


  • Cell Cycle Proteins
  • RNA, Messenger